The enzyme-linked immunospot assay (ELISpot) is widely used for the detection of T-cell specific responses. In the ELISpot assay, T-cells secreting a specific cytokine are detected by incubating the T-cells in an ELISpot assay plate on which antibodies specific for the cytokine are immobilised. Cytokine bound to the antibodies can then be visualised using standard immunoassay procedures. Spots of bound cytokine localised in areas of the assay plate where cytokine production has occurred indicate the presence of activated T-cells. Since each spot represents cytokine production by a single cell, if the number of cells present in the assay plate are known, the frequency of responding cells can be ascertained by counting the number of spots formed.
The ELISpot assay has also been used for other purposes such as the detection of virus infected cells, the enumeration of cells secreting specific antibody, the detection of cells secreting fibronectin and the study of monocytes.
The use of soluble cofactors to enhance the detection of positive cells in the ELISpot assay has been described. Immobilised cofactors have been used to stimulate T-cells and the presence of cytokines in the culture medium has subsequently been detected by ELISA-based analysis.